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(No Model.) 4 Sheets-Sheet 1.

B. M. WILKERSON.

DENTAL CHAIR.

No. 419,299. Patented Jan. 14,1890.

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(No Model.) 4 Sheets-Sheet 2.

- R M. WILKERSON.

. DENTAL GHAIR.

No. 419,299. Patented Jan. 14, 1890.

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(N0 Modl.) 4Shets-Sheet 3.

'B. M. WILKERSON.

DENTAL CHAIR. No. 419,299. Patented Jan. 14, 1890,

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-13. M'WILKE RSON. DENTAL CHAIR.

Patented Jan. 14, 1890;.

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' UNITED STATES PATENT OFFICE.

BASIL M. WVILKERSON, OF BALTIMORE, MARYLAND, ASSIGNOR TO THE S. S.

WHITE DENTAL MANUFACTURING COMPANY, OF

SYLVANIA.

PHILADELPHIA, PENN- DENTAL CHAIR.

SPECIFICATION forming part of Letters Patent No. 419,299, dated January14, 1890.

Application filed October 11, 1887. Serial No. 251,982. (No model.) I

To all whom. it may concern.-

Be it known that I, BASIL M. WILKERsoN, of the city of Baltimore, in theState of Maryland, have invented certain new and. useful Improvements inDental Chairs, of which the following is a specification.

My present invention relates to improvements in dentists chairs, whichin some respects include features the same as or more or less nearlyresembling parts shown and described in my prior applications, Nos.7,392 and 8,822, respectively filed December 21, 1877, and March 14,1879; and it consists in certain novel constructions and combinations ofmechanism made the subject of claims based upon the followingdescription, with reference to the accompanying drawings, in which-Figure 1 is a side elevation of the chair. Fig. 2 is a rear elevationthereof. Fig. 3 is a sectional view of the tilting mechanism. Fig. 4 isa side elevation, partly in section, on the line a zof Fig. 6, showingthe elevating mechanism. Fig. 5 is a vertical section on theline cc wofFig. 4; and Fig. 6 is a horizontal section on the line 3 y, Fig. 4..Fig.7 is a crosssection through the supporting-plunger and surroundingparts on the line 12 c, Fig. 4.. Fig. Sis a side elevation, partly insection, of a modification of the elevating mechanism. Fig. 9 is asimilar view of another modification thereof, and Fig. 10 is a verticalsection of the elevating mechanism of Fig. 9. Fig. 11 is 'an'elevation,partly in section, of still another modification of the elevatingmechanism; and Fig. 12 is a section-through the mechanism of Fig. 11 onthe line a a of said figure. Fig. 13. is a view of another modificationof the elevating mechanism; and Fig. 14 is an elevation, partly insection, of a modification of the automatic brake or lowering mechanism.

Fig. 15 is a vertical sectional view of the headrest and itsattachments. Figs. 16 and 17 are transverse sectional views of the same,and Fig. 18 is a plan View of the supporting-bar. Fig. 19 is across-section of the supportingbar on the line 10 w of Fig. 15. Figs. 20and 21 are respectively plan and sectional views of the swinging andsliding link of the head-rest devices. Fig. 22 is a rear elevation ofthe head-rest pad and some of its conneccaSing or housingand details ofthe rotary tions. Figs. 23 and 24 are sectional views of modified formsof the clamp actuating or locking devices of the head-rest. Fig. 25 is aView in elevation, showing a portion of the friction-brake mechanism.

A is the chair frame or body, which is mounted upon a suitable base Aand is'pivoted at a to one side ofthe vertically-adjust able support orplunger B. The chair-frame carries a gear-rack a, curved in the arc of acircle described about the pivot a as a center, and through therack-plate of thechair-frame passes a screw Z), holding the plateclosely, but without binding, against lugs formed on the side of theplunger, (see Fig. 3,) a slot a being formed in the plate for thepassage of the screw 1; to allow of a rocking movement of thechair-frame about its pivot a. A Wormgear 0, mounted in suitablebearings secured to the plunger, engages with the segmental rack-platea. The worm-gear shaft carries a bevel gear-wheel c, which engages witha similar wheel 0 upon the shaft 0 which has attached a crank 0 and hasits bearings carried by the chair-frame. Upon turning the crank, motionis communicated to the worm, which, meshing with "the teeth upon thesegment-plate a, causes the chair-body to tilt in a vertical plane uponthe pivot a. The angle of inclination of the chair-body is thus readilyadjusted as may be desired. 1

Inasmuch as it is sometimes required to tilt the chair-bodymore rapidlythan can conveniently be doneby rotating the crank c mechanismisprovided for throwing the worm C out of gear with the segmentalgear-rack, and consists of the following elements: A stud-shaft d. (seeFig. 3). is rigidly attached to the plunger B, and upon it is mounted ancecentric-wheel (1 to which is attached a lever or handle D. Theeccentric-wheel rotates between lugs or bearing projectioLrisict aboveand below it upon a bracket or plate fadj ustable upon the plunger andcarryin lie bear- ID ':i ings for the worm-wheel.v The worm-carrylugbracket is rendered adjustableby being slotted, so that it may slide upand down upon the screws that attach to it the plunger-B.

The stud (Z carries a spring (1'', that engages a with the lever D andnormally holds the worm" and rack gearing in engagement. Upon depressingthe lever the worm is carried down, leaving the chair-body free to berapidly tilted upon its pivot a by direct application of force. As thelever is released, the worm again rises, gearing with and securing thesegment-rack to maintain the chair-frame as adjusted.

The parts thus far described relate to the tilting mechanism andconstitute the first part of my invention. The second part of myinvention, next to be described, relates to the mechanism for elevatingand lowering the chair-body.

E is a housing or casing which contains the mechanism for verticallymoving the chair-body, and is mounted on the base A, in which it iscapable of rotation. A screw actuated by alever L passes through thebase and is adapted to clamp the casing, when desired, to preventrotation. The plunger B slides vertically in the front of the casing Eand has on its rear side a gear-rack B.

Vithin the casing is mounted in suitable bearings Z Z a shaft 1,carrying a small bevel gear-wheel M, which meshes with a similar butlarger wheel M. Upon the shaft of the latter is a pinion m, that drivesa wheel m, whose shaft also carries a pinion N, that drives the largewheel 12. The pinion a, mounted upon the shaft of the latter, engageswith the rack B.

The construction and arrangement of the train will readily be understoodfrom Figs. 4, 5, and 6 of the drawings, whence it will be seen that asshaft Z is revolved the plunger is raised or lowered. Above the pinion nis a second pinion e, which also engages with the rack and has a disk 6'fixedly mounted on its shaft at the end thereof opposite that to whichthe pinion is secured. This shaft is allowed slight up-and-down andsidewise play in its bearing a adjacent to the pinion. The disk islikewise allowed movement in its slotted bearing e The disk revolveswith the shaft freely in its bearing in the casing E (see Figs. 1, 4t,5, and (i) as the plunger is raised.

Owing to the inclination of the outer or rearincst wall of the slottedbearing 6 the pressure upon the disk as the plunger descends causes itto act as a friction-brake and automatically regulate the descent of theplunger, the friction being, of course, in proportion to the weight.This descent is therefore practically uniform whatever be the weight ofthe chair-body and occupant.

E is a casing in front of the plunger, and contains the locking-block 19that is thrust after the manner of a knee-joint against the face of theplunger by a rod 19 adjusted by means of a set-screw Q and jam-nut,essentially as shown and described in my beforementioncd application No.8,822 of March 14, 187 9.

To unlock the plunger, it is only necessary to lift the block 19 whichin this instance is effected by means of a rod 19, threaded foradjustment at 19 where it is provided with a nut, upon which the block11 rests, and actuated by a lever p, pivoted at P and provided with afoot-plate F at either side of and extending below the casing E. Asecond brake is provided in the shape of a strap 0, that is brought tobear on the disk 0 on the shaft Z as the lever 19 is depressed and theblock 19 lifted. A spring is secured in the casing E and engages with alug q near the lower end of the plunger when the latter reaches the endof its upward stroke. The shaft 1 is driven, as will presently bedescribed, by a treadle, and terminates in a clutch-section R,

that is adapted to interlock with a clutchsection R on the shaft f,which latter is slid back and forth to throw the clutch into and out ofgear by means of a foot-plate S, attached to a rod 0'', which is pivotedto the end of a lever r, fulcrumed at r". The upper end of this lever isconnected in well-known way to the clutch member R to slide it on itsshaft While leaving it free to revolve. The rod '1" is provided with alug that slides in slot S in the lower part of the casing E,which isprovided with a series of detent depressions or holes 8 at the side ofthe slot. A spring 0 attached to the rod 7'', snaps into one or other ofthese depressions and holds the parts normally in position,whileadmitting of their being moved by the foot-plate S when sufficient forceis applied to cause the spring to yield and become disengaged from its(letent-hole.

As shown, the foot-plate and cooperating parts of the clutch-controllingmechanism are duplicated, so as to be actuated from either side of thechair.

To prevent reverse motion of the gearing should the plunger be rapidlyelevated and at the end of its stroke encounter the springstop q, thedriving mechanism is arranged to be automaticallly thrown out of gear,this being accomplished as the beveled lip (1 on the lower end of theplunger encounters the end of the rod Q, which is pivotally connectedwith the sliding part R of the clutch. As this occurs, the rod Q ispushed back, disengaging the parts of the clutch.

As before stated, the shaft Z is driven by a treadle, which, as shown,is made part of a dental engine. The shaft f is mounted in bearings inthe end of the casing E and in a rigid support 6 exterior to the fly anddriving wheel F, where it has the usual crank f, connecting-rod f andtreadle f The crank-pin H is attached by a spring h to an arm 71 locatedto one side of the support, this being the usual means for preventingthe wheel from stopping on the centers. The end of the connecting-rod fis threaded at g and enters a nut pivoted to the forward end of thetreadle, whereby the length of the rod may be adjusted. The treadle f ispivoted at g to a block which is attached by means of a rod G to thelower end of the support 6, where it is pivoted at g. Thus the treadlemay be moved to either side of the chair, as the operator may desire.

To the upper end of the support 6 is pivoted at t a yoke, through whichpasses a tube I, slotted, as shown at 1'. The tube carries at its lowerend a rubber disk t", that presses against a groove in the face of thewheel F. This groove is curved transversely in the arc of a circledescribed about the pivot 2' so that the disk is maintained in contactwith the groove as the chair is tilted. Within the tube slides ortelescopes the rigid shaft J of the dental motor-cable j, which isprovided with the usual hand-piece 7. A sleeve it embraces the rod J,and is attached to the chair-back by a pivoted bar K, the object beingto enable the rod J to fall back with the chair-back as the chair istilted. It will be seen that the longitudinal motion of the shaft fnecessary to throw the clutch R B into gear disengages the disk 2" fromthe wheel F, so that the elevating mechanism and drill-shaft cannotoperate simultaneously.

The third part of my invention relates to the head-rest, which isillustrated in a general way in Figs. 1 and 2, and more particularly inFigs. 15 to 22, inclusive.

Modifications, in turn to be described, of the locking devices for thehead-rest clamp-link and its vertically adjustable support are shown inFigs. 23 and 24.

On the chair-back is a dovetail rib t,' embraced by a main supportingsliding bar T, having a correspondingly-shaped longitudin al groove.Through the main bar passes a thumbscrew t, which engages with the rib tand holds this bar in any position to which it is adjusted by raising orlowering it. The upper end of the bar T is provided with the supportingplate or head 25 for the head-restcarrying link or bar U,-which platehas a longitudinal slot 25 The-carrying bar or link U is a hollow'orslotted casing, the slot extending longitudinally thereof and from topto bottom or vertically therethrough, and one of thelongitudinally-extending bounding-walls of the link-slot beinginclined.(See Figs. 16, 17, 20, 21, 23, and 24.)

U is an adjustable cover-plate or top section for the link U, and has adepending rib U which projects into the link-slot, extends parallel withthe inclined bounding-wall thereof, and on its face opposite said wallis inclined cor-respondin gly therewith. In the space interveningbetween said rib and slot-wall is a tapered block u, made in two parts,Figs. 20 and 21, and having a headed pin u, passing through its centralaperturel It is obvious that as the pin is. drawn downward thebeveledfaces of the block u, acting on the inclined wall of thelink-slot and-the similarlyinclined rib of the cover-plate, will causethem to spread apart. The rib U is beveled at one end in a line inclinedto the longitudinal axis of the main bar or link section U, and this endbears against a correspondingly-inclined shoulder a at the end of theslot in themain link-section U. (See Figs. 20 and 21.) Obviously, anyspreading of the link-pieces, or transverse motion as regards eachother, causes longitudinal motion of the upper part U relatively to thelower part U. This longitudinal motion is a desideratum, as the oppositeend of the rib U is beveled, as at u and acts upon a block U whichconstitutes one part of a divided bearing or socket in the end of thelink-bar U, clamping the ball Von the end of the head-rest stud v.

The longitudinal motion of the parts U U which results 'in clamping theball V is brought about as follows: Through the pin u passes a shaft 15having acam that, as the shaft is rotated, presses against the lowerface of the head or plate t of the main supporting-bar T. To the shaft19 is pivoted lever T of the clamp-locking devices, that is normallyheld by a spring T close to the chair-back. The operation of these partswill readily be understood from Figs. 1, 2, 15, 16, 17, 18, 20, and 21,it being obvious that as the lever is turned in one direction the pin ais retracted and the head-rest link clamped tightly on the top of theplate t the ball V being at the same time secured as above described,and that when the lever is turned in the opposite direction to loosenthe clamp the link may swivel or turn about the pin to as well as slidelongitudinally, and also have a transverse slidingmovement imparted toit by adj ustlnent of the pin in the slot t of the supporting-bar heador top plate. Were this transverse movement of the link dispensed with,an opening of a size only sufficient for the free passage of the pin awould be provided in the supporting-bar top plate in lieu of theelongated slot i WV is the head-rest pad, which is properly upholsteredand is fastened eccentrically, as shown in Figs. 2 and 22, to aradially-corrugated platet. A similarly-formed plate '0 is made integralwith the stud r,to which the ball V is affixed, and a thumb-screw esecures the plates together. An arm-rest for the operator swivels on abar 20, that terminates in a slotted plate 10 Fig. 22. This plate isprovided on either side with a rib 20?, that engages with thecorrugations on the plates Q1 t the thumb-screw Q23 passing through theslot and clamping the plate 20 tightly to the head-rest. Thisconstruction admits of a motion of the arm-rest to and from thehead-rest, while the pad, being eccentrically secured to the plate 1/,may be adjusted vertically or laterally by a simple revolution about thescrewo In case the arm-rest is dispensed with, the corrugations on theplates 22 o engage with each other and hold the head-rest firmly. g

In Figs. 11 and 12 of thedrawings is illustrated a modification of theelevating mechanism, the plunger being shown as threaded and embraced bya collar, also threaded to engage the plunger, and actuated by a bevelgear-wheel meshing therewith and mounted on the fly-wheel shaft.

In Figs. 9 and 10 worm-gearing is substituted for bevel-gearing, thecollar for engaging the plunger resting 011 bearings and subserving thefunction of a brake to regulate the descent of the plunger, the wormbeing, of course, thrown out of gear.

In Fig. 13 aworm is substituted for the pinion that engages with therack on the plunger, and in Fig. 8 a worm is substituted for the bevelgear-wheel that communicates motion to the train.

In Fig. 14 is shown a modification of the automatic or self-regulatingfriction brake hereinbefore described. A hollow plunger contains a swiftpitched screw 6, that revolves in a threaded collar inside the plunger.A cone on the end of the screw rests in a socket in the chair-base. Asthe plunger descends, the screw is made to revolve, the resistance (1'.6., the friction between cone and socket.) being in proportion to theweight imposed.

Figs. 23 and 24 illustrate certain modifications of the locking orsecuring devices for the head-rest clamp-link and its supportingbar,designed to secure the supporting-bar to the chair-back by the sameoperation that ti ghtens the joints of the head-rest linl'gwhich link isthe same as before described. In Fig.

23 the clamp-lever is shown as actuating a screw that bears upon theretracting-pin u at an angle to the length thereof. The thrust of theclamp-screw here retracts the pin and at the same time jams the end ofthe pin against the rib on the chair-back, and so locks it againstvertical movement. In Fig. 2a the clamp-screw actuated by the levercarries a cam 00, that enters a slot as in the barac which latter has aninclined bearing y at its lower end for the adj Listin -screw y. As thelever is turned, the pin u is retracted and the bar a clamps the supportto the chair-back. It will be seen that in these modifications theoperation of the clamp-link upon the ball of the head-rest stud is thesame as hereinbefore fully described.

It will not be out of place here to briefly advert to the peculiaradvantages arising from the several details of construction, ashereinbefore described, as well'as to the important results incidentupon the combinations of parts. Being pivoted to one side of theplunger, as shown in Figs. 1, 2, and 3, the chair-body is prevented fromrattling on its support, as all lost motion is taken up in onedirection. The worm-wheel furnishes a ready means of regulating theangle of inclination and adjusting it exactly as may be desired, and,being adapted to be thrown out of gear in an instant, facility isafforded for rapidly tilting the chair. This latter feature is ofespecial importance, as when teeth are extracted while the patient isunder the influence of an anaesthetic there is danger of strangulationfrom the blood flowing into the throat. The advantage of a means forreadily and rapidly bringing the patient to an upright position in theevent of such a contingency will be appreciated. I do not herein claimthis feature, broadly, as it is so claimed in my before-mentioned priorapplication, filed December 21, 1877.

The mechanism for elevating the plunger is thoroughly efficient inoperation, and its salient feature consists in imparting to the plungera continuous vertical movement through the medium of mechanism actuatedby a foot-lever or treadle. Incidentally this treadle is made a part ofthat indispensable article in a dentists office, the dental engine. Thedescent of the plunger is automatically controlled by the disk e restingon its bearing e or by some such equivalent, as the friction-screw shownin Fig. 14. Obviously, friction being proportional to pressure, therapidity of descent is theoretically independent of the weight of thechair-seat and its occupant, and practice in this respect coincides withtheory, or nearly so. The clutch f, &c., securely grips the plunger (itis made the subject of a claim in my abovementioned application filedMarch 14, 1879, No. 8,822) and holds it in any position to which it israised. On its release the plunger is free to descend, but may bearrested by the brake O 0, &c., the same serving as a check on theautomatic friction device a in case the latter should from any causerefuse to act properly.

The automatic disengagement of the clutch R R has already beensufficiently set forth, as well as its object and function.

The dental engine is made a part of the chair and is carried with thebody in its revolution 011 the pedestal wherein the movable part islocked by a screw actuated by the lever L.

The treadle of the engine swivels freely at g and g and may be moved toeither side of the chair, as the operator desires, without impairing theefliciency either as a motor for the engine or as the means of actuatingthe elevating mechanism. The pivot gbein g under the treadle forward ofthe heel of the operator, positive motion is imparted throughout thedownward and upward strokes of the rod f The engine is always handy foruse, is never in the way, and is adapted for use in any possibleposition of the chair-b0dy.

The handle of the head-rest clamp is preferably pivoted, as shown, andis normally held by a spring T close 'to the chair-body, the objectbeing to keep it out of the way and prevent its catching in the clothingor wateh-guard of the operator as he passes from side to side of thechair.

By the term vertical as used hereinbefore and in the claims, inconnection with the elevating and lowering of the chairframe, head-rest,&c., I do not propose, of course, to restrict myself to the communicating of such motions in lines absolutely perpendicular or inabsolute right lines. A slightinclination, even if not desirable, is ofno material disadvantage.

I do not claim herein anything shown in my prior applications ofDecember 21, 1877, and March 14, 1879, hereinbefore referred to, nor theparticular construction and organization by which the chair and engineare combined, as these will be claimed in another application to befiled by me.

WVhat I claim is 1. The combination of the chair-frame, its supportingbar or plunger, the curved rack secured to the chair-frame, the worm forengaging said rack, and the worm carrying bracket vertically adjustableupon the plunger, substantially as and for the purpose set forth.

2. The combination, substantially as set forth, of thechair'frame-supporting bar or plunger, the rotary friction-brake, itsshaft, the gearing connecting said shaft with the plunger, and thecasing provided with thein clined slotted bearing for thefriction-brake, whereby said brake is thrown into action upon thedescent of the plunger and controls its movement.

3. The combination, in a dental chair, of the elevating devices thereof,the swiveling operating-treadle for actuating said devices, and thesupport connected with the chair and to which the treadle is jointed andrendered movable into operative position at either side of the chair,substantially as and for the purpose set forth. I

4. The combination of the chair-frame-supporting bar or plunger, thedriving mechanism for elevating it, provided with the clutch devicesconsisting of clutch-sections and the rod for disengaging theclutch-sections, said rod having, connection at one end with one of saidsections and operated upon at its opposite end and moved endwise inglink adj'ustabl'y supported on said plate, having thelongitudinally-extending slot passin g therethrough vertically or fromtop to bottom, a pin passing through the supportingbar head and throughsaid link-slot and about which the link swivels and slides, the lookingdevices to clamp said pin and link together i and to secure thesupporting-bar in position, and the head-rest pad carried and clamped bythe link, substantially as set forth.

6. The combination of the two-part link, the one part sliding relativelyto the other, the stud of the head-rest pad provided with the ballmounted in a divided bearing in the link, the divided block in the link,the vertically-adj ustable pin engaging said block, and means forclamping these parts in position, substantially as set forth.

7. The combination, in a head-rest, of the two-part link having a socketand with the one part sliding relatively to the other, the head-reststud having the ball for engagement with said socket, the bar upon whichthe link is adj ustably secured and relatively to which the link bothslides and turns horizontally and which is vertically adjustable on thechair-back, and the locking devices by which to operate the slidingsection of the link to clamp the ball of the head-rest stud, and alsolock the link and bar in position, substantially as set forth.

8. The combination of the head-rest stud provided with the ball, thetwo-part link adjustably supported upon the top of and turning andsliding relatively to a vertically-adjustable support at the chair-backand having a-socket, and with the one part of the link slidingtransversely and longitudinally relatively to the other to clamp theball carried by the head-rest stud in said link, and the clampingdevices for locking the parts in their adjusted positions, substantiallyas set forth.

In testimony whereof I affix my signature in presence of two witnesses.

BASIL M. WVILKERSON.

Witnesses:

'JNo. T. MADDOX, SEPTIMUS BUNTING.

